Dynamical breakdown of the Ising spin-glass order under a magnetic field

TL;DR

This study investigates the dynamical magnetic behavior of an Ising spin glass under various magnetic fields, revealing a phase transition only in zero field and supporting droplet theory predictions for finite fields.

Contribution

It provides experimental evidence for the absence of a spin-glass phase transition in finite magnetic fields, supporting droplet theory over mean-field predictions.

Findings

Spin-glass phase transition occurs only at zero magnetic field.

Data interpreted by droplet theory suggests no transition in finite fields.

Relaxation times depend on temperature and static magnetic field.

Abstract

The dynamical magnetic properties of an Ising spin glass Fe$_{0.55}$Mn$_{0.45}$TiO$_3$ are studied under various magnetic fields. Having determined the temperature and static field dependent relaxation time $\tau(T;H)$ from ac magnetization measurements under a dc bias field by a general method, we first demonstrate that these data provide evidence for a spin-glass (SG) phase transition only in zero field. We next argue that the data $\tau(T;H)$ of finite $H$ can be well interpreted by the droplet theory which predicts the absence of a SG phase transition in finite fields.